1. Field of the Invention
This invention relates to dibenzoanthracene derivatives suitably usable as organic materials for organic electroluminescent devices, electroluminescent devices making use of the electroluminescent derivatives, and display apparatus making use of the electroluminescent devices.
2. Description of the Related Art
As self-emitting flat panel displays of low power consumption, high response speed and no viewing angle dependency, display apparatus making use of organic electroluminescent devices (so-called organic EL devices) have been drawing attention in recent years.
An organic electroluminescent device is provided between an anode and a cathode with an organic layer, which contains an organic light-emitting material capable of emitting light when a current is fed. Developed as such organic layers include, for example, a construction that a hole transport layer, a light-emitting layer with an organic light-emitting material contained therein, and an electron transport layer are stacked one over another from the side of the anode, and a construction that a light-emitting material is included in an electron transport layer to form an electron-transporting, light-emitting layer.
Organic electroluminescent devices of such a construction are self-emitting devices. When constructing a display apparatus by using these organic electroluminescent devices, it is, therefore, most important requirements to provide them with a longer service life and to ensure their reliability. Accordingly, research is now under way on organic materials that make up organic electroluminescent devices.
Concerning materials equipped with the anthracene skeleton among such organic materials, numerous derivatives have been investigated such as anthracene derivatives and bisanthracene derivatives having one or more amino or aryl groups and anthracene derivatives having one or more styryl groups. For example, refer to Japanese Patent Laid-open Nos. 2003-146951 (Patent Document 1), Hei 09-268284 (Patent Document 2), Hei 09-268283 (Patent Document 3), 2004-67528 (Patent Document 4), and 2001-284050 (Patent Document 5) for more information.
For example, Patent Document 1 discloses the use of 2,6-disubstituted 9,10-diarylanthracene compounds, each of which contains aryl groups substituted to the 9- and 10-positions of anthracene and also particular substituent groups introduced to the 2- and 6-positions of anthracene, as materials for forming hole transport layers. Among the materials for forming hole transport layers, aromatic amine compounds equipped with fluorescence are described to be usable as materials for light-emitting layers. Patent Document 2, on the other hand, discloses that compounds containing arylamino groups substituted to the 9- and 10-positions of anthracene can be effectively used as light-transmitting materials.
In the meantime, a variety of investigations have also been made on organic light-emitting materials capable of emitting blue, green and red colors, respectively, with a view to realizing a full color display on a display apparatus that makes use of organic electroluminescent devices. Regarding blue-light emitting materials, in particular, further improvements are required in color purity, luminescence efficiency and light-emitting life. Accordingly, improvements are now underway, for example, with respect to stilbene, styrylallene and anthracene derivatives. For more information, refer to Non-patent Document 1 (Materials Science and Engineering: R: Reports, 39(5-6), 143-222 (2002)) and Non-patent Document 2 (Applied Physics Letters (USA), 67(26), 3853-3855 (1995)), for example.